Bryobia, Koch, 1836

Mirza, Jawwad Hassan, Elgoni, Nasreldeen Ahmed, Kamran, Muhammad & Alatawi, Fahad Jaber, 2025, Mites of the genus Bryobia (Acari, Tetranychidae): taxonomic notes on some species and a diagnostic key to the world species, ZooKeys 1239, pp. 51-73 : 51-73

Subgenus Bryobia s. str. Koch, 1836

Type species.

Bryobia praetiosa Koch, 1836: 8 .

Diagnosis

(based on females). As defined by Mirza et al. (2024).

Key to the 43 species of the subgenus Bryobia

Species groups definition is based on Mirza et al. 2024

Notes on the species of the subgenus Bryobia

The subgenus Bryobia includes 53 species ( Mirza et al. 2024), although only 43 species are included in the key above. Among the remaining ten, two species belong to the species group praetiosa , B. geigeriae Meyer, 1974 , and B. karooensis Meyer, 1974 , which are excluded from the key due to ambiguity in the leg I true claw morphology as debated by Mirza et al. (2024). The two species B. (B.) calida Karg, 1985 and B. (B.) lagodechiana Reck, 1953 could not be assigned to any species group due to insufficient information available on the position of the inner sacral seta f 1. The status of the remaining six species excluded from the above key is discussed below.

Species group praetiosa

The species B. (B.) montana Mitrofanov, 1973 was originally described from Tadjikistan on the host plant Astragalus sp. , while the species B. (B.) nitrariae He & Tan, 1993 was reported from China on the host plant Nitraria sibirica . These two species are similar in all morphological characters, including leg chaetotaxy. The only difference is in the number of setae on tarsus I for both species, 20 vs 18, respectively. The descriptions of both species provided leg setal counts as the total number, including sensory and tactile setae. It is important to note that He and Tan (1993) differentiated B. (B.) nitrariae from B. (B.) tadjikistanica Livschits & Mitrofanov, 1968 , which is also morphologically close to B. (B.) montana . The two species, B. (B.) tadjikistanica and B. (B.) montana , share the same type locality, Tadjikistan. There are also minor differences between B. (B.) nitrariae and B. (B.) tadjikistanica in the shape of their spermathecae and true claws. The two species B. (B.) montana and B. (B.) nitrariae key out near each other. Examining the type specimens would help to clarify their statuses.

The three species, B. (B.) graminum ( Schrank, 1781) , B. (B.) monticola Wang, 1985 , and B. (B.) neopraetiosa Meyer, 1974 are also morphologically close. They have been reported from Germany (on Poaceae sp.), China (on Poaceae sp.), and South Africa (on multiple hosts), respectively. The leg chaetotaxy for B. (B.) neopraetiosa is neither described nor illustrated in detail (except for femur I, genua I and II, and tibia I), while that of B. (B.) graminum and B. (B.) monticola has few variations on leg tarsal segments. Based on the available descriptions, re-descriptions, and illustrations, it could be suggested that B. (B.) monticola and B. (B.) neopraetiosa should be synonymized with B. (B.) graminum . Similarly, the species B. (B.) exserta Wang, 1985 was reported from China on Artemisia sp. and was distinguished from B. (B.) praetiosa Koch, 1836 based on minor morphological variations, including body length, propodosomal lobe lengths, leg genu I segment comparative lengths. Bryobia (B.) exserta also morphologically resembles the three species discussed above. It is impossible to decide the synonymy of B. (B.) exserta , whether it should be synonymized with B. (B.) graminum or B. (B.) praetiosa . The species B. (B.) praetiosa is the type species of the genus Bryobia , while B. (B.) graminum , one of the oldest species described, was moved to the genus Bryobia by Oudemans (1929). Mitrofanov et al. (1987) synonymized B. (B.) praetiosa with B. (B.) graminum , but previously, Pritchard and Baker (1955) considered synonymizing B. (B.) praetiosa with B. (B.) graminum and suggested further detailed studies. However, these two species still remain valid ( Migeon and Dorkeld 2025).

Two species, B. (B.) qinghaiensis Ma & Yuan, 1981 and B. (B.) yunnanensis Ma & Yuan, 1981 , are described from China, from the Palearctic and Oriental regions, respectively. They are morphologically similar to each other, apart from some setal variations on leg tarsal and tibial segments, and were differentiated from B. (B.) praetiosa and B. (B.) qinghaiensis , respectively, based on a few minor differences. These species resemble B. (B.) praetiosa , the type of the genus. Note that the concept of a praetiosa species complex still exists, and there are a considerable numbers of populations described under the name of praetiosa , or otherwise, from different localities of the world. Each of those descriptions and illustrations provided various degrees of chaetotaxies and body measurements, which further complicate the true identification of B. (B.) praetiosa . Pritchard and Baker (1955) provided an excellent debate on the overall situation of the praetiosa complex. It appears that this complex and its synonyms will continue to grow.

The species B. (B.) batrae Baker & Tuttle, 1994 was described from the USA, occurring on the host plant Stellaria media . This species cannot be added to the key as it was very briefly described and illustrated. Baker and Tuttle (1994) also did not compare it with any related species. The species B. (B.) japonica Ehara & Yamada, 1968 , also cannot be included as it was also very briefly described. The authors did compare it with B. (B.) sarothamni and B. (B.) tadjikistanica based on the absence of dorsal lobes. These two species belong to the subgenus Allobia (Bryobia) ( Mirza et al. 2024) .

Tuttle and Baker (1976) described B. (B.) neoribis with a duplex on both leg tarsi III and IV. However, their 1994 original description of the species on Acer negundo from Utah, USA stated an absence of duplex on leg tarsus IV. Based on the current designations, the latter species / population belongs to the subgenus Lyobia (Bryobia) . The authors further stated that this species was similar to the European B. (B.) ribis Thomas, 1896 . The latter is poorly described and has been suggested as a synonym of B. (B.) praetiosa ( Pritchard and Baker 1955) . This population of B. (B.) neoribis should be reidentified based on type material examination to reach a valid species designation.

The two species, B. (B.) neoribis sensu Tuttle and Baker (1976) and B. (B.) ribis are morphologically close. Mathys (1957) provided detailed morphological analysis and bioecological aspects of the species B. (B.) ribis and other Bryobia species found in the French part of Switzerland. The species B. (B.) neoribis was differentiated from B. (B.) ribis based on the number of setae on the femur I (24 vs 16) and variations in body and setal lengths. Tuttle and Baker (1976) did not provide a comprehensive description of the species, preventing detailed comparison and validation with other Bryobia species. Similarly, there is no detailed description and illustration of B. (B.) ribis . Mathys (1957) stated that complementary morphological differences could be found in the larval stage of B. (B.) ribis . This raises doubts over the validity of B. (B.) neoribis as only the female stage was briefly described. It would require a comprehensive set of specimens from the type locality to validate the status of the B. (B.) neoribis . For the time being, both species are excluded from the diagnostic key.

The species B. (B.) xizangensis Wang, 1985 was described from China from an unknown host plant. This species was originally differentiated from B. (L.) longisetis Reck, 1947 and was described with one or two pairs of tenent hairs on leg empodium I. Based on the findings of the present study, this species could be morphologically close to B. (B.) hengduanensis Wang & Cui, 1991 due to one pair of tenent hairs present on empodium I, but differentiated based on the length of dorsal body hairs, short vs long, crossing the bases of setae next in line, respectively. Considering the two pairs of tenent hairs on empodium I, B. (B.) xizangensis is similar to B. (B.) ziziphorae Strunkova & Mitrofanov, 1983 , but is easily differentiated based on the development of propodosomal lobes, strongly developed and deep incision between the inner and outer lobes vs. weakly developed with small lobes, respectively.

Figures

Figure 6. Shape of dorsal setae in adult female a palmate in Bryobia (Lyobia) alveolata Auger & Flechtmann, 2009 (redrawn from Auger et al. 2009) b fan-shaped in Bryobia (Lyobia) kakuliana Reck, 1956 (redrawn from Livschitz and Mitrofanov 1971) c spatulate in Bryobia (Allobia) birivularis Meyer, 1989 (redrawn from Meyer and Ueckermann 1989) d lanceolate in Bryobia (Lyobia) gushariensis Livschits & Mitrofanov, 1971 (redrawn from Livschits and Mitrofanov 1971) e setiform serrate in Bryobia (Lyobia) cinereae Auger & Migeon, 2014 (redrawn from Auger and Migeon 2014).